The high-latitude Sodankylä research station hosts high-quality infrastructure in the boreal zone. It supports several programs exploring upper-air chemistry and physics, atmospheric column measurements, cryospheric and hydrological processes, biosphere–atmosphere interaction and satellite calibration–validation studies. This special issue aims to address the breadth of research infrastructure and its utilization as well as to facilitate future innovative multi-disciplinary research through integrated monitoring.

Lamp measurements used for the UV irradiance calibration of two Brewer spectrophotometers operated for 20 years in Jokioinen and Sodankylä, Finland, were examined. Temporal development of the responsivity after fixing the irradiance measurements into a specific scale was studied. Both long-term gradual decrease and abrupt changes in responsiveness were detected. Frequent-enough measurements of working standard lamps were found necessary to detect the short-term variations in responsiveness.

FMI's combined road weather station (RWS) and roadside unit (RSU) in Sodankylä is a unique research platform combining very advanced road weather measurements with a versatile collection of the most common wireless communication methodologies used in a vehicular environment. Together with harsh Arctic road weather conditions it represents an incomparable development environment and pilot RWS station within the field of intelligent transport systems and vehicular networking.

Digital photography has become a widely used tool for monitoring the vegetation phenology. The seasonal cycle of the greenness index obtained from photographs correlated well with the CO2 exchange of the plants at our wetland and Scots pine forest sites. While the seasonal changes in the greenness were more obvious for the ecosystem dominated by annual plants, clear seasonal patterns were also observed for the evergreen forest.

The paper describes the history and the present state of instrumental seismic observations at the University of Oulu and Sodankylä Geophysical Observatory in northern Finland that started in 1950s. This includes both seismic observations at permanent seismic stations and temporary seismic experiments by portable seismic equipment. We describe the instrumentation and major research topics of seismic group at the SGO and discuss the plans for their future development.

The paper described an extensive in situ data set of bulk snow depth, snow water equivalent, and snow density collected as a support of SnowSAR-2 airborne campaign in northern Finland. The spatial and temporal variability of these snow properties was analyzed in different land cover types. The success of the chosen measurement protocol to provide an accurate reference for the simultaneous SAR data products was analyzed in the context of spatial scale, sample size, and uncertainty.

Solar spectral UV irradiance data measured by the Brewer #037 spectroradiometer in Sodankylä, Finland, in 1990–2014 were examined for their quality flags given by the quality assurance (QA) tools of the European UV DataBase (EUVDB). Statistical analysis on the flags was performed, and five cases were investigated in detail. The results can be used in further development of the quality control/QA tools and selection of cases of exceptional atmospheric conditions for process studies.

This paper describes the laboratory facilities at the Finnish Meteorological Institute – Arctic Research Centre (FMI-ARC). They comprise an optical laboratory, a facility for biological studies, and an office. The facilities are ideal for responding to the needs of international multidisciplinary research, giving the possibility to calibrate and characterize the research instruments as well as handle and store samples.

In this paper we describe a new method for recognition of digits in seven-segment displays. The method is used for adding date and time information to a dataset consisting of about 7 million auroral all-sky images taken during the time period of 1973–1997 at camera stations centred around Sodankylä observatory in Northern Finland. In each image there is a clock display for the date and time together with the reflection of the whole night sky through a spherical mirror.

Carbon dioxide is the most abundant greenhouse gas emitted due to human activities. Changes in atmospheric columns of carbon dioxide can be measured accurately using ground-based Fourier transform spectrometers, which are operating in the near-infrared spectral region. Our measurements at Sodankylä reveal a significant increase of column carbon dioxide since the start of the column measurements at Sodankylä in early 2009.

The Sodankylä Geophysical Observatory has been producing ionospheric tomography data since 2003. Based on these data, one solar cycle of ionospheric vertical total electron content (VTEC) estimates is constructed. The measurements are compared against the IRI-2012 model, F10.7 solar flux index and sunspot number data. Qualitatively the tomographic VTEC estimate corresponds to reference data very well, but the IRI-2012 model are on average 40 % higher of that of the tomographic results.

We use the connection between auroras and geomagnetic field variations in a concept for a Regional Auroral Forecast (RAF) service. RAF is based on statistical relationships between alerts by the NOAA Space Weather Prediction Center and magnetic time derivatives measured by five MIRACLE magnetometer stations located in the surroundings of the Sodankylä research station. As an improvement to previous similar services RAF yields knowledge on typical auroral storm durations at different latitudes.

In this paper, a 26-year-long time series of total ozone column above Arctic Research Center in Sodankylä is presented. The time series is produced using a uniform method, presented in the paper, for retrieving the ozone column from the measurements. The data are checked for obvious errors and filtered automatically and manually to ensure that only good-quality data are delivered to public databases. Some features of the time series are highlighted and availability of the measurements is presented.

Physically based models that predict the properties of snow on the ground are used in many applications, but meteorological input data required by these models are hard to obtain in cold regions. Monitoring at the Sodankyla research station allows construction of model input and evaluation datasets covering several years for the first time in the Arctic. The data are used to show that a sophisticated snow model developed for warmer and wetter sites can perform well in very different conditions.

We describe the steps that are used at the Finnish Meteorological Institute (FMI) to process spectral ultraviolet (UV) radiation measurements made with its three Brewer spectrophotometers, located in Sodankylä (67° N) and Jokioinen (61° N). Multiple corrections are made to the data in near-real time and quality control is also performed automatically. Several data products are produced, including the near-real-time UV index and various daily dosages, and submitted to databases.

The manual snow survey program of Finnish Meteorological Institute consists of numerous observations of natural seasonal snowpack in Sodankylä, in northern Finland. Systematic snow measurements began in 1911 with snow depth and snow water equivalent. In 2006 the manual snow survey program expanded to cover snow macro- and microstructure from snow pits. Extensive time series of manual snow measurements are important for the monitoring of temporal and spatial changes in seasonal snowpack.

At the Finnish Meteorological Institute in Sodankylä and the Danish Center for Hydrology, calibration functions for organic surface layers were derived for two in situ soil moisture sensors to be used in the validation of coarse-resolution soil moisture from satellites and land surface models. There was no clear difference in the data from a variety of humus types, strengthening confidence that these calibrations are applicable over a wide range of conditions as encountered in the large areas.

A comprehensive, distributed network of in situ measurement stations gathering information on soil moisture has been set up in recent years at the Finnish Meteorological Institute's (FMI) Sodankylä Arctic research station. The network is used as a tool to evaluate the validity of satellite retrievals of soil properties. We present the soil moisture observation network and the results of comparisons of top layer soil moisture between 2012 and 2014 against ESA CCI product soil moisture retrievals.

The paper presents the initial findings of the Arctic Snow Microstructure Experiment in Sodankylä, Finland. The experiment observed the microwave emission of extracted snow slabs on absorbing and reflecting bases. Snow parameters were recorded to simulate the emission upon those bases using two different emission models. The smallest simulation errors were associated with the absorbing base at vertical polarization. The observations will be used for the development of snow emission modelling.

Sodankylä, in the heart of the Arctic Research Centre of the Finnish Meteorological Institute in northern Finland with temperatures ranging from −50 to &plus;30 °C, provides a challenging location for numerical weather forecasting (NWP) models. In this article, the use of measurements performed in Sodankylä for near-real time online verification of NWP models is described. A more specific case study of three different radiation schemes, applicable in NWP model HARMONIE-AROME, is also presented.

Ionograms from the Sodankylä Geophysical Observatory ionosonde (station SO166) were scaled automatically with the Autoscala software during a test period. The results were compared with manually scaled ionospheric parameters. In general, the F-layer parameters were found to agree well, whereas high-latitude phenomena like auroral E layers were often misidentified.